Regional Refined Grid Modeling of Acidic and Mercury Deposition over Northeastern US and the Contribution of New York Power Point Sources.

Leon Sedefian1, Michael Ku2, Kevin Civerolo3, Winston Hao4 and Eric Zalewsky5

The importance of atmospheric processes and the response of the underlying land and water surface to  anthropogenic air pollutant input has been studied considerably and as recent EPA and New York State (NYS) policy and regulatory approaches have emphasized an interest in the interaction of multi-pollutant mixtures, the need for more comprehensive approaches has surfaced. These requirements have been supported by technical documents with heavy reliance on regional photochemical modeling assessments.  Many national and NYS requirements affect the emissions and interactions of pollutants from energy production sources such as Energy Generation Units (EGUs) and waste to energy (WTE) facilities.  However, technical assessments to carry out these requirements and to understand the multi-pollutant system have not been commensurate with the latest emissions data and the techniques or approaches necessary to properly assess the implementation of these requirements. 

The purpose of the current study was to address the limitations in previous regional modeling assessments by refining the previous coarse grid resolutions down to a 4km grid level in an novel application of the Community Multiscale Air Quality (CMAQ) Eulerian grid modeling system on an annual timescale, using the latest available National Emissions Inventory (NEI) for 2011 and Weather Research and Forecasting (WRF) simulated meteorological data.  The other emphasis was to determine the contribution of the NYS major power generation sector point sources to the overall acidic and mercury depositions. For mercury, emissions of the elemental, oxidized and particulate species were characterized using available data to properly characterize the contribution of EGUs and WTE facilities. 

The results of the CMAQ modeling for annual and some seasonal deposition levels for the 2011NEI and the power sector are presented in graphical forms over the modeling domain and, in particular, over NYS.   The results show the importance of both dry and wet deposition for the oxidized form of mercury which has the largest contribution to the total mercury levels.  The contribution of the NYS’s power sector is deemed relatively small and very localized, with the impact of emissions outside the modeling domain clearly dominating total Hg depositions, confirming the importance of regional transport into the state.  For acidic deposition, the importance of wet deposition is noted for sulfates and nitrates, but dry deposition becomes dominant for total sulfur deposition.   The larger summer versus winter contributions for sulfate is noted, but for mercury or nitrates, no real distinction by season is found.  The emissions from the NYS power sector is determined to have the largest effect in reducing total sulfur deposition, but not for the other species.  In addition, projected “future” year reduction in EGUs and other source emissions cause large reductions in both sulfate and nitrate levels.  A comparison of wet deposition observations at NADP monitors to CMAQ results indicates remarkably good model performance for mercury and acidic deposition species.


1SEDEFIAN Consulting,
2New York State Department of Environmental Conservation, Albany NY
3New York State Department of Environmental Conservation, Albany NY
4New York State Department of Environmental Conservation, Albany NY
5New York State Department of Environmental Conservation, Albany NY